For integrals, we would say that "b and a are the limits of integration".

The notation "lim x->0 1/x" would be read as "the limit of 1 over x as x goes to zero." In general, "lim" is short for "limit" of whatever follows it, with respect to what is below the "lim" symbol. Rarely, I have also seen the notation "l.i.m." used for the limit in mean, i.e. the limit with respect to the L^2 norm.